1. Field of the Invention
This invention relates to a disc cartridge having a shutter member for opening/closing a recording and/or reproducing aperture formed in a main cartridge body unit rotationally housing a disc-shaped recording medium, such as a magnetic disc.
2. Description of the Related Art
Heretofore, there is employed a disc cartridge comprised of a main cartridge body unit, made up of upper and lower cartridge halves, abutted and connected to each other, and a magnetic disc rotationally housed therein, in which the main cartridge body unit has a recording and/or reproducing aperture for exposing at least a portion of the signal recording region of the magnetic disc housed in the main cartridge body unit to outside along the radius of the disc.
This type of the disc cartridge is provided with a shutter member formed by warping a thin metal sheet and which is adapted for opening/closing a recording and/or reproducing aperture provided in the main cartridge body unit. This shutter member has a pair of shutter portions for opening/closing the recording and/or reproducing apertures formed in the upper and lower surfaces of the main cartridge body unit, and a connecting piece interconnecting these shutter portions. The shutter member is U-shaped in cross-section and is attached to the main cartridge body unit by being fitted on a lateral side of the main cartridge body unit.
The shutter member, attached to the main cartridge body unit, has a guide piece engaging in a movement guide groove formed in the upper or lower surface of the main cartridge body unit. This guide piece, engaged in the movement guide groove formed in the upper surface or in the lower surface of the main cartridge body unit, is formed by vertically segmenting a portion of the shutter portion. The shutter member is mounted on the main cartridge body unit, in a manner free from extrication from the main cartridge body unit, by having the guide piece engaged in the movement guide groove. Also, the shutter member is moved by the guide piece being guided along the movement guide groove so that the shutter member is supported on the main cartridge body unit for movement in a direction of opening/closing the recording and/or reproducing aperture along a lateral surface of the main cartridge body unit.
Meanwhile, the shutter member is configured so that, when the shutter member adapted for opening/closing the recording and/or reproducing aperture is mounted on the main cartridge body unit, it can moved along the upper and lower surfaces of the main cartridge body unit without being protruded from the upper and lower surfaces of the main cartridge body unit. That is, the shutter member is configured to have the above-mentioned U-shaped cross-section, with the interval between the facing shutter portions being approximately equal to or slightly smaller than the thickness of the main cartridge body unit.
The movement guide groove, formed in the upper surface or in the lower surface of the main cartridge body unit, is formed by having a portion of the upper or lower surface of the main cartridge body unit swollen inwards. Therefore, the movement guide groove is formed for extending at a site offset from the magnetic disc housing section along the lateral side of the main cartridge body unit along which the shutter member is moved. The purpose of providing the movement guide groove is to narrow the space within which to accommodate the magnetic disc to prevent obstruction of magnetic disc rotation in the main cartridge body unit.
Therefore, the guide piece engaged in the movement guide groove is formed on the connecting portion of the shutter member to the connecting piece corresponding to the proximal end o the shutter member. Since the guide piece is used to prevent extrication of the shutter member from the main cartridge body unit, it is of a height sufficient to prevent the guide piece from being detached easily from the movement guide groove when the guide piece is engaged in the groove.
If the shutter member of the U-shaped cross-section, with a thickness substantially equal to the thickness of the main cartridge body unit and a height sufficient to prevent the guide piece from being detached easily from the movement guide groove, is to be mounted on the main cartridge body unit, the portion of the shutter member carrying the guide piece is thrust open and flexed such as to reduce the thickness of the lateral side of the main cartridge body unit carrying the shutter member.
However, if the proximal end side of the shutter member carrying the guide piece is extended open excessively, the shutter portion extended from the connecting piece is deformed, as a result of which the shutter portions are floated from the upper or lower surfaces of the main cartridge body unit to render it impossible to reliably open or close the recording and/or reproducing aperture when the shutter member is attached to the main cartridge body unit.
In a lateral side of the main cartridge body unit carrying the shutter member, there is formed a gap via which a torsion coil spring for biasing a shutter member mounted on the main cartridge body unit in the direction of closing the recording and/or reproducing aperture is inserted into the main cartridge body unit. The portion of the gap can be easily flexed and deformed, however, the remaining portions of the main cartridge body unit cannot be flexed and deformed easily because of the abutting upstanding wall sections of the upper and lower cartridge halves making up the main cartridge body unit.
The plural guide pieces of the shutter member are provided at large distances on both sides of the movement direction of the shutter member to permit stable movement of the shutter member along the lateral side of the main cartridge body unit. Thus, when mounting the shutter member on the main cartridge body unit, the totality of the guide pieces cannot be caused to face the portions of the main cartridge body unit that can be flexed and deformed easily. The result is that, when the shutter member is attached to the main cartridge body unit, one or more guide pieces are caused to face the readily flexible portions of the main cartridge body unit, as a result of which the guide pieces and the lateral surface of the main cartridge body unit are overlapped to render it difficult for the guide pieces to be engaged in the movement guide groove. If, as the guide pieces are overlapped with the lateral surface of the main cartridge body unit, the shutter member is thrust into the main cartridge body unit so that the guide pieces will be engaged in the movement guide grooves, the guide pieces or the shutter portion carrying the guide pieces are flexed and deformed into engagement in the movement guide grooves. However, this scrapes off a portion of the main cartridge body unit to produce chips, while damaging and impairing the appearance of the main cartridge body unit. Moreover, if chips produced from the main cartridge body unit are affixed to the magnetic disc, dropout of information signals occurs frequently when recording and/or reproducing the information signals. In addition, the guide pieces or the shutter portions formed with the guide pieces are flexed severely, while the shutter member itself is deformed to render it impossible to reliably close the recording and/or reproducing aperture in the main cartridge body unit.